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Meeting the threat from space

What do an asteroid and a tsunami have in common? Plenty, it turns out.

It seems one of the toughest issues for politicians to address in a timely way is a natural hazard with potentially catastrophic consequences but whose risk of actually occurring is highly uncertain. For a moment, think about the tsunami that left about 230,000 people dead or missing around the Indian Ocean basin. Scientists there and abroad were aware of the tsunami risk. Even a rudimentary tsunami warning system, combined with effective public risk education, could have saved many lives. But faced with other pressing challenges — poverty, for one — the countries hardest hit by the disaster chose not to address the looming but uncertain tsunami risk.

Now consider the risk that an asteroid will strike Earth and kill perhaps hundreds of thousands of people — or worse. We know it has happened. We know it will happen again. And we've found some of the likeliest future perpetrators. One that has been in the news and on Astronomy.com quite a bit is 99942 Apophis, a 20-billion-kilogram hunk of space rock with a 1-in-45,000 risk of hitting Earth April 13, 2036 — mark your calendars down for a sick day — somewhere from Siberia to the west African coast. Likely hazard: devastating Pacific Rim tsunamis. Look out, California.

So, here we are faced with the uncertain risk of an event that could bring catastrophic tsunamis. Some concerned experts attending the meeting this week in San Francisco of the American Association for the Advancement of Science called for the United Nations to create a process by which the world's nations can decide when and whether to act when faced with an asteroid threat. We would have plenty of time to send a heavy spaceship, or "gravitational tractor," to perturb an asteroid's orbit slightly — just enough so that it misses Earth.

Or we could wait to see if the tsunami happens, although that didn't work very well for Indonesia in 2004. With the major near-Earth asteroid surveys locating more and more potentially dangerous space rocks, it's time for policymakers in the United States and Europe, who have done such a great job of assessing the asteroid threat, to pony up the money to fund a serious planetary-defense system.